We present a sample of 221 new quasar pairs with proper transverse separations R prop < 1 h -1 Mpc over the redshift range 0.5 < z < 3.0, discovered from an extensive follow-up campaign to find companions around the Sloan Digital Sky Survey and 2dF QSO Redshift Survey quasars. This sample includes 26 new binary quasars with separations R prop < 50 h -1 kpc (θ < 10″), more than doubling the number of such systems known. We define a statistical sample of binaries selected with homogeneous criteria and compute its selection function, taking into account sources of incompleteness. The first measurement of the quasar correlation function on scales 10 h -1 kpc < R prop < 400 h -1 kpc is presented. For R prop ≲ 40 h -1 kpc, we detect an order of magnitude excess clustering over the expectation from the large-scale (R prop ≳ 3 h -1 Mpc) quasar correlation function, extrapolated down as a power law (γ = 1.53) to the separations probed by our binaries. The excess grows to ∼30 at R prop 10 h -1 kpc and provides compelling evidence that the quasar autocorrelation function gets progressively steeper on submegaparsec scales. This small-scale excess can likely be attributed to dissipative interaction events that trigger quasar activity in rich environments. Recent small-scale measurements of galaxy clustering and quasar-galaxy clustering are reviewed and discussed in relation to our measurement of small-scale quasar clustering.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science